I am passing along the single best advice that I received from my sister's oncologist.
Get the feeding tube sooner rather than later. For me that was the raditation halfway point. You as his loving caregiver will know when/if a feeding tube is necessary.
For me the tube was a lifesaver because I could get my nutrition without pain. I insisted that all of my meds could be taken by tube and I could get enough water to avoid dehydration. And, if you have a Vitamix you can inrake some awesomely nutritious smoothies that will aid the healing process.
I was on the tube for 6 months and have zero regrets. My treatment team was against it and I still dont understand why but I am glad that I insisted on it when I did. I firmly believe the feeding tube made the treatment and healing less traumatic.
Treatment is hard but doable.